Many designs have been considered for launching an orbital launch vehicle from a carrier aircraft. The designs which have been considered include carrying the launch vehicle on top of the carrier aircraft, on the bottom of the aircraft, under the aircraft wing, towing the launch vehicle behind the aircraft, and carrying the launch vehicle within the cargo area inside the aircraft. Launching a launch vehicle from a carrier aircraft, while having some limitations in terms of maximum gross weight of the launch vehicle, has many operational advantages. Launching from a carrier aircraft avoids the costs and limitations associated with ground-based launch ranges. Ranges may have restrictions limiting the number of launches which can be performed in a given time frame. At a typical rocket range, launches will be limited with respect to the launch azimuth which can be flown by the necessity of avoiding overflight of densely populated areas. A launch vehicle which is launched from a carrier aircraft, on the other hand, can be based anywhere where the carrier aircraft can be based. A carrier aircraft also has the advantage that it can be used to avoid unfavorable weather by flying around or over a weather system. For low-cost launch systems, the cost of using a national range in the United States can exceed 30 percent of total costs associated with a particular launch. The limitations associated with fixed ranges have caused at least one supplier of launch services to fly vehicle launches from a floating ocean platform, and another supplier of launch services to use a carrier aircraft where the launch vehicle is attached beneath the carrier aircraft or beneath the carrier wing.
Air launch can also provide a performance benefit based on the velocity of the carrier aircraft which is imparted to the launch vehicle at the time of separation from the carrier aircraft. Performance benefit is also gained by reduction in aerodynamic drag. Such drag can be substantially decreased by operating the launch vehicle at an initial starting altitude which is above one half to three quarters of the atmosphere. Reduced atmospheric pressure can increase performance of the first stage engine by allowing a greater area ratio between the rocket engine throat and the expansion bell. Reduced atmospheric pressure also allows the use of a lower engine chamber pressure, which, particularly in the case of a pressure fed vehicle, can result in substantially decreased structural weight for the propellant tanks.
In the past large airborne payloads, including in one case, a test missile, have generally been extracted from the air cargo bay along with a cradle on which the payload rests, by parachutes released into the air stream behind the carrier aircraft. This known approach has several disadvantages including high loadings caused by the substantial extraction loads, and the need to expend or recover the extraction cradle. Furthermore, the extraction parachutes, followed by orientation parachutes, substantially eliminate the forward velocity of the launch vehicle, thus limiting the benefit which is gained from the air launch. What is needed is an apparatus and method for dropping a launch vehicle from a carrier craft which minimizes loads on the launch vehicle and which minimizes loss of forward velocity, and which eliminates the need for a drop cradle.